Jared Padalecki plays Sam Winchester (right), one of the stars of the series Supernatural. The Winchester brothers also star in the series-within-the-series, which is -- meta alert! -- also called Supernatural. Here, Sam talks to the (fictional) series author at a (fictional) convention for (fictional) rabid fans.

David GrayThe CW

How do you measure love?

OK, it's a huge question. And maybe not one generally applied to television. But the metrics of success determine whether a television show lives or dies. (If this is the sort of topic that seems frivolous, consider the billions of dollars TV and other copyright industries contribute to the U.S. economy. The stakes start feeling higher.)

And this is why we're looking at the CW show Supernatural. Unlike a massively popular scripted TV show like The Big Bang Theory or The Walking Dead, it has only about 3 million viewers. Its Nielsen ratings are, frankly, not that great. Yet Supernatural has lasted for nine seasons (so far), partly because its fan base makes up in engagement what it lacks in size. Supernatural has almost as many "likes" on Facebook as NCIS, a show with an audience six times larger.

That Supernatural's leads are two preternaturally handsome young men, of course, doesn't hurt. They're blogged about on Tumblr more than almost any other actor except for Benedict Cumberbatch. But it takes more than sex appeal to achieve such fan activation. Fans appreciate the show's complicated plotting, its rich world of details and its unanswered questions. That's all fodder to argue about on message boards and explore in fan fiction. What kind of powers does a fallen angel have? What were the main characters like as children? Is a sexy demon a good sexy demon or a badsexy demon?

Supernatural is the second most popular TV show on fan fiction's biggest website. And Supernatural fan fiction has been penned by no less of a literary personage than S.E. Hinton, who's much better known for authoring classic young adult novels, including The Outsiders and That Was Then, This Is Now. She enjoys fan fiction's anonymity, so she refused to offer any clues about how to find hers.

"If you come across one that's just really good, that's mine," she told NPR.

Now, it's not unusual for fans to write fiction about their favorite TV shows. It's veryunusual for TV shows to write scripts about their fans. Supernatural's writers intentionally incorporate the show's fandom back into the program's plot. So in the show, there's a series of books, called Supernatural, based on the adventures of the main characters. The Supernatural books have fans ... on the show, Supernatural. Those fictional fans hold Supernatural fan conventions, where they dress up as the main characters on the show ... while interacting with the characters on the show. Obviously, it gets staggeringly meta.

"Supernatural takes it to a whole other level," says Lynn S. Zubernis, a psychologist, professor and co-author of Fangasm, a book about Supernatural fans. "The sort of reflexive dialogue it has going on with its fandom."

Zubernis says Supernatural even dares to gesture toward slash fiction — the sort of fan fiction, usually written by women, that imagines a homoerotic relationship between a show's male characters. (On Supernatural, that's especially loaded. The characters are brothers whose last name is Winchester, so this kind of slash is called "Wincest" by fans. And it's probably why Supernatural's publicists did not return any of my emails seeking comments by the show's writers about fan engagement.)

This kind of dialogue between show and fan might seem novel, says English professor Katherine Larsen, the other author of Fangasm. But look back through literature, she suggests. Great stories have always inspired a powerful sense of ownership from enthusiastic fans.

"Charles Dickens changes the end of Great Expectations because the fans were not happy," she offers as example. And Sir Arthur Conan Doyle had to resurrect Sherlock Holmes in the face of fan outrage after their beloved detective died.

"So fans have had this kind of power for longer than we've had a really good sense of them having that power," she says.

"Nielsen has done a lot of research as to whether social media is helping people to tune in to TV," he says, noting that a show's traction on Twitter and Tumblr is starting to affect how networks pitch shows to the all-important advertisers. "They're no longer just including Nielsen ratings. They're also including social TV data."

Fan engagement gives color and volume to dry data, such as ratings, but the question remains, how do you quantify depth of feeling? Writing a story takes longer and means more than hitting a "like" button or re-blogging a picture. How do you measure a kind of success that, by its very nature, is completely resistant to metrics?

Copyright 2014 NPR. To see more, visit http://www.npr.org/.

Transcript

AUDIE CORNISH, HOST:

Next, a story about one of the biggest shows on TV: "Supernatural." All right, to be clear, it doesn't have spectacular ratings but the fans who do watch are remarkably passionate and engaged. Case in point, on Facebook, "Supernatural" has almost as many likes as "NCIS," a show with six times the audience.

NPR's Neda Ulaby reports on the novel ways the show engages with fans.

NEDA ULABY, BYLINE: Fans say they love "Supernatural" for its complicated plots and great big heart, and because it's about two really hot guys who hunt monsters.

(SOUNDBITE OF TV SERIES, "SUPERNATURAL")

JENSEN ACKLES: (as Dean Winchesters) Sam?

JARED PADELECKI: (as Sam Winchesters) Dean?

(SOUNDBITE OF MUSIC)

ACKLES: (as Dean Winchesters) Sam, look out.

(SOUNDBITE OF MUSIC)

ULABY: Sam and Dean are brothers. Their mom was tragically killed by a demon, so they drive around Middle America hunting down ghosts, chupacabras, even the occasional fallen angel.

(SOUNDBITE OF TV SERIES, "SUPERNATURAL")

MISHA COLLINS: (as Castiel) You two need to be more careful.

ACKLES: (as Dean Winchesters) Yeah, I'm starting to get that.

COLLINS: (as Castiel) Lucifer is circling his vessel. And once he takes it, those hex bags won't be enough to protect you.

LYNN ZUBERNIS: It's such a complex mythological world.

ULABY: Lynn Zubernis is a psychologist, professor and "Supernatural" super fan. She co-wrote a book about "Supernatural" fandom. It's called "Fangasm." She says fans help the show score multiple People Choice Awards and the cover of TV Guide and Entertainment Weekly. On Tumblr, its stars get more reblogs than almost anyone than Benedict Cumberbatch. What "Supernatural" offers fans is a world rich in details.

ULABY: The show inspires arguments on message boards and hundreds of thousands of pages of fan fiction. Fans come up with their own stories exploring what kind of powers a fallen angel might have, what were the brothers like as kids or is a character a good sexy demon or a bad sexy demon.

(SOUNDBITE FROM TV SERIES "SUPERNATURAL")

UNIDENTIFIED MAN #2: She's a demon, Sam, period.

UNIDENTIFIED MAN #3: They want us dead. We want them dead.

UNIDENTIFIED MAN #4: Look what she did to you. She's poison, Sam.

ULABY: This tiny TV show is now the second most popular program on fan fiction's biggest website. Among the contributors, at least one famous author.

S.E. HINTON: My name is Susan Hinton and I'm very much a "Supernatural" fan.

ULABY: S.E. Hinton is better known for writing "The Outsiders" and "That Was Then, This Is Now." Fan fiction is generally anonymous and she's cagey about how to find hers.

HINTON: If you come across one that's just really good, that's mine.

ULABY: Lots of shows have fan fiction. What's different about "Supernatural" is how its writers incorporate its fandom back into the TV show. It gets really meta. So on the show, there are "Supernatural" fan gatherings like the ones in real life.

UNIDENTIFIED MAN #5: Welcome to the first annual "Supernatural" convention.

ULABY: Complete with the kind of fans who dress up and pretend to be the main characters.

UNIDENTIFIED MAN #6: You guys are larping, aren't you?

UNIDENTIFIED MAN #7: Excuse me?

UNIDENTIFIED MAN #6: You're fans.

UNIDENTIFIED MAN #7: Fans of what? What is larping?

UNIDENTIFIED MAN #6: Live action role play.

ZUBERNIS: "Supernatural" takes it to a whole other level, the sort of self reflexive dialogue that it has going on with its fandom.

ULABY: Lynn Zubernis says most shows barely acknowledge fans, but "Supernatural" even gestures towards slash fan fiction. Slash is often written by women and imagines a sexual relationship between the show's male characters.

ULABY: "Supernatural's" fictional characters are brother whose last name is Winchester so people call this kind of slash fiction Wincest. Wincest is probably why the show's publicists declined to return my emails. This kind of meta dialogue between show and fan might seem new says English professor Katherine Larson. She's the other writer of the book, "Fangasm." But she says look back through literature.

Great stories have always inspired ownership from enthusiastic fans.

KATHERINE LARSON: Charles Dickens changes the end of "Great Expectations" because the fans are not happy.

ULABY: And Sir Arthur Conan Doyle had to resurrect Sherlock Holmes in the face of fan outrage when he died.

LARSON: So fans have had this kind of power for longer than we've had a really good sense of them having that power.

ULABY: But how can that power serve a TV show economically today? "Supernatural's" empowered articulate fans have supported it through nine seasons. Mike Prouix wrote a book about social media and television.

MIKE PROUIX: Nielsen has done a lot of research as to whether or not social media is helping to drive people to tune in to TV.

ULABY: Social media may have helped improve "Supernatural's" recent ratings. Prouix says the shows traction on Twitter and Tumblr is starting to effect how networks pitch shows to advertisers.

PROUIX: They're no longer just including Nielsen ratings. They're also including social TV data.

ULABY: That engagement lends color and volume to data like ratings, but how do you quantify a depth of fan feeling? When a "Supernatural" fan writes a story, it takes longer and means more than re-blogging a picture. That's an unsolved problem for television, how to measure a kind of success, a kind of loyalty and love, that resists conventional metrics. Neda Ulaby, NPR News. Transcript provided by NPR, Copyright NPR.